Dimercury(I)-Induced Stable G-Quadruplex Based Supramolecular Polymers and Gels Outperforming Conventional G₄ K

Guanosine (G) historically facilitates G-quartet assembly, a non-canonical DNA secondary structure primarily stabilized by K⁺ ions. Herein, it is reported that mercurous ion (dimercury(I), [Hg-Hg]²⁺, G:Hg⁺ = 1:0.5-1.5) forms a significantly more stable G-quadruplex G₈·Hg₂ ²⁺ than the well-known G₄·K⁺. G₈·Hg₂ ²⁺ self-assembles in water through J-type stacking via an isodesmic mechanism, creating stable supramolecular polymers (SPs) crosslinked to produce thermo-reversible self-healing hydrogels. Dimercury(I) more efficiently promotes the formation of G-quadruplex SP with enhanced stability, which is evident from its higher tolerance to aging, dilution, and temperature. This enhanced stability is attributed to the covalent Hg⁺─Hg⁺ bond, which holds two G-tetrads together, thereby greatly stabilizing the octameric G-quadruplex G₄·Hg⁺-Hg⁺·G₄ and exhibiting a significantly higher binding energy than G₄·K⁺·G₄, as determined computationally. Despite this enhanced stability, G₈·Hg₂ ²⁺ SP gel exhibits excellent anion responsiveness, either breaking or solubilizing the G-quadruplex SP, unlike G₄·K⁺ gel. Moreover, at higher metal ratios (Hg⁺ > 1.5), a thermodynamically stable [G₂·(Hg₂ ²⁺)₂] dimeric assembly is formed, whereas mercuric ion (Hg²⁺) supported dimeric complexation G₂·Hg²⁺ ₂ regardless of the metal ratio. These results suggest that Hg ions, irrespective of their oxidation state (I/II), have a strong affinity for binding with G, potentially providing insights into the molecular basis of Hg's genotoxicity.